Telogen effluvium is a common, temporary form of hair shedding that happens when something pushes a large number of follicles into the resting phase all at once. A couple of months later, those hairs let go together, which is why the shedding can feel sudden and alarming. The reassuring part is that it is usually temporary: the follicles are not destroyed, and in most cases hair regrows once the trigger is resolved. At True Roots in La Canada Flintridge, evaluation is physician-led by board-certified Dr. Luis Valle.
What is telogen effluvium?
Your hair cycles through growth, transition, and rest, and normally only about 10 to 15 percent of your hair sits in the resting (telogen) phase at any time. Telogen effluvium occurs when a stressor abruptly shifts many more follicles into that resting phase simultaneously. Those hairs stay put for a couple of months, then shed together when new growth pushes them out. The result is a noticeable, diffuse increase in shedding across the whole scalp, not a bald patch or a receding line.
Why the shedding seems to come from nowhere
The most confusing feature of telogen effluvium is timing: the shedding shows up about two to three months after the trigger, by which point you may have forgotten the event that caused it. Common triggers include:
- A high fever or significant illness
- Surgery or general anesthesia
- Childbirth (see postpartum and menopausal hair loss)
- Major physical or emotional stress
- Rapid weight loss or crash dieting
- Starting or stopping certain medications
- Thyroid dysfunction or iron deficiency
Because of the delay, connecting the shed to its cause often takes a little detective work, which is part of what an evaluation helps with.
How long does it last?
Acute telogen effluvium usually resolves within about three to six months after the trigger is removed, with full density often returning over six to twelve months as the follicles cycle back into growth. If shedding continues beyond six months, it is considered chronic and deserves evaluation for an ongoing cause, such as a thyroid problem, persistent iron deficiency, or a continuing stressor. The distinction matters because acute cases mostly resolve on their own, while chronic ones usually have something fixable driving them.
Will your hair grow back?
In most cases, yes. Because telogen effluvium pushes follicles into rest rather than killing them, hair typically regrows once the underlying trigger is addressed, over several months to about a year. The best things you can do are identify and resolve the trigger, correct any deficiency, and be patient while the cycle recovers. If it does not improve, or if it is layered on top of genetic thinning, a physician can sort out what else is contributing.
When to get evaluated
See a physician if your shedding is heavy or lasts beyond about six months, if it comes with other symptoms like fatigue or weight changes, or if you are not sure whether it is temporary shedding or something more. An evaluation with targeted bloodwork (iron, ferritin, thyroid, and more) can identify a treatable cause and distinguish telogen effluvium from pattern hair loss, which sometimes coexists. For the full picture of possible causes, see what is causing my hair loss.
Telogen effluvium versus pattern hair loss
It helps to know which you are dealing with:
- Telogen effluvium: sudden, diffuse shedding all over, usually after a specific trigger, and temporary.
- Pattern hair loss: gradual, patterned (receding hairline or widening part), genetic and progressive.
If genetic thinning is also present, treatments like the FoLix laser address that component, while the telogen effluvium itself typically resolves with time and trigger removal. A consultation can tell you which mix applies.
This article is educational and not a substitute for personalized medical advice.